/*
 *  Copyright 2019-2020 somewhere
 *
 *  Licensed under the Apache License, Version 2.0 (the "License");
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *  http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */
package com.albedo.java.common.core.util;

import javax.crypto.Cipher;
import javax.crypto.SecretKey;
import javax.crypto.SecretKeyFactory;
import javax.crypto.spec.DESKeySpec;
import javax.crypto.spec.IvParameterSpec;
import java.nio.charset.StandardCharsets;

/**
 * 加密
 *
 * @author somewhere
 * @date 2018-11-23
 */
public class EncryptUtil {

	private static final String STR_PARAM = "Passw0rd";

	private static Cipher cipher;

	private static IvParameterSpec iv = new IvParameterSpec(STR_PARAM.getBytes(StandardCharsets.UTF_8));

	private static DESKeySpec getDesKeySpec(String source) throws Exception {
		if (source == null || source.length() == 0) {
			return null;
		}
		cipher = Cipher.getInstance("DES/CBC/PKCS5Padding");
		String strKey = "Passw0rd";
		return new DESKeySpec(strKey.getBytes(StandardCharsets.UTF_8));
	}

	/**
	 * 对称加密
	 */
	public static String desEncrypt(String source) throws Exception {
		DESKeySpec desKeySpec = getDesKeySpec(source);
		SecretKeyFactory keyFactory = SecretKeyFactory.getInstance("DES");
		SecretKey secretKey = keyFactory.generateSecret(desKeySpec);
		cipher.init(Cipher.ENCRYPT_MODE, secretKey, iv);
		return byte2hex(
			cipher.doFinal(source.getBytes(StandardCharsets.UTF_8))).toUpperCase();
	}

	/**
	 * 对称解密
	 */
	public static String desDecrypt(String source) throws Exception {
		byte[] src = hex2byte(source.getBytes(StandardCharsets.UTF_8));
		DESKeySpec desKeySpec = getDesKeySpec(source);
		SecretKeyFactory keyFactory = SecretKeyFactory.getInstance("DES");
		SecretKey secretKey = keyFactory.generateSecret(desKeySpec);
		cipher.init(Cipher.DECRYPT_MODE, secretKey, iv);
		byte[] retByte = cipher.doFinal(src);
		return new String(retByte);
	}

	private static String byte2hex(byte[] inStr) {
		String stmp;
		StringBuilder out = new StringBuilder(inStr.length * 2);
		for (byte b : inStr) {
			stmp = Integer.toHexString(b & 0xFF);
			if (stmp.length() == 1) {
				// 如果是0至F的单位字符串，则添加0
				out.append("0").append(stmp);
			} else {
				out.append(stmp);
			}
		}
		return out.toString();
	}

	private static byte[] hex2byte(byte[] b) {
		int size = 2;
		if ((b.length % size) != 0) {
			throw new IllegalArgumentException("长度不是偶数");
		}
		byte[] b2 = new byte[b.length / 2];
		for (int n = 0; n < b.length; n += size) {
			String item = new String(b, n, 2);
			b2[n / 2] = (byte) Integer.parseInt(item, 16);
		}
		return b2;
	}
}
